In the field of prosthetics and orthotics, artificial limbs can be used by people who have lost an arm, leg, hand or other portion of a limb. A person who is born without a limb, or who has lost a limb due to accident or disease, may use an artificial limb to perform tasks and activities of a human limb. Amputees may retain a portion of a limb known as a “residual limb.” A prosthetist can create a plaster mold of the residual limb and use this mold to create a custom “hard socket” that is worn by the amputee. The prosthetist generally attaches the custom hard socket to the artificial limb using laminate or other means in the art at the distal end of the hard socket. The hard socket and the artificial limb are connected to make up a single piece of equipment. A prosthesis, orthosis, or exoskeleton is known as an “assistive device.”
An amputee may put on (or “don”) a prosthetic liner before donning the hard socket. A prosthetic liner fits in a hard socket like a sock fits in a shoe. The liner helps maintain a proper fit of the residual limb in the hard socket, reduces pressure points, reduces skin irritation and provides additional benefits. As such, for proper support of the artificial limb, the liner must fit well and be secured within the hard socket. Thus, a user of an artificial limb needs a way to easily attach and detach the hard socket/artificial limb component from the liner. When the attachment mechanism is inside the hard socket, the user cannot see or necessarily feel the attachment mechanism. Additionally, because a liner stretches when it is placed over a residual limb, it has a tension force that resists pulling in the distal direction and makes attachment to a hard socket more difficult for the amputee. An attachment mechanism that allows a simple attachment of the liner to the hard socket is needed.
Some artificial limbs are powered and can be controlled by a microprocessor. One such limb, known as a myoelectric prosthesis, uses its microprocessor to translate electrical signals from the user's remaining muscles into command signals that are transmitted to different components of the artificial limb. Myoelectric assistive devices generally require a system that allows for transmission of electrical signals from the user's muscles to the assistive device. One liner for myoelectric assistive devices is described in R. Lipschutz, D. Tkach, B. Lock, L. Hargrove, and T. Kuiken, Systems and Methods of Myoelectric Prosthesis Control, U.S. patent application Ser. No. 13/587,755, filed Aug. 16, 2012, which is incorporated by reference.
In the prior art, different prosthetic liner connectors are known. One such example of liner connectors are pin locks which involve the use of a threaded rod screwed, on the distal end, into an embedded female thread and mechanically locked on the other end into the prosthesis. The connector acts as a mechanical pin and can have different styles such as rastered, clutch, smooth and ball bearing. The pin provides purely a mechanical connection and does not pull in the liner within the prosthesis until it is already physically engaged. (The words “distal” and “proximal” are used to identify relative distance from the user. A “proximal” end of a component is located closer to the user, while a “distal” end of the component is located further from the user.)
Prior art attachment systems such as the Maglock (ST&G Corp., Brea, Calif.) or the MagnoFlex Lock (Ottobock, Germany) provide assisted donning and a mechanical attachment between the liner and a prosthesis, but the systems do not provide the electrical connectivity required by a myoelectric assistive device.
Furthermore, in the prior art, compliance components, such as washers, are not necessarily used to support two connecting magnets. If the compliance components oscillate 180 degrees out of phase, the oscillation may break the magnetic connection between the two magnets. If an electrical signal passes between the magnets, oscillation could similarly break the electrical connection and result in the loss of electrical signal.